• Korean Journal of Mathematics
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• v.24 no.3
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• pp.537-543
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• 2016

Let D be an integral domain, X be an indeterminate over D, D[X] be the polynomial ring over D, and D(X) be the Nagata ring of D. Let [d] be the star operation on D[X], which is an extension of the d-operation on D as in [5, Theorem 2.3]. In this paper, we show that D is a sharp domain if and only if D[X] is a [d]-sharp domain, if and only if D(X) is a sharp domain.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.2
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• pp.335-353
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• 2017

This paper presents the application technique on thrust jacking pressuring of shield TBM in the sharp curved tunnel alignment by model tests. Recently, the application of shield TBM method as mechanized tunnelling is increasing to prevent the vibration and noise problems, which can be occurred in the NATM in the urban area in Korea. However, it is necessary to plan the sharp curved tunnel alignment in order to avoid the building foundation and underground structures, to develop the shield TBM operation technique in the shape curved tunnel alignment. Therefore, the main operation parameters of shield TBM in the curved tunnel alignment are reviewed and analyzed based on the case study and analytical study. The results show that the operation of shield jacking force system is the most important technique in the shape curved tunnel alignment. The simplified scaled model tests are also carried out in order to examine the ground-shield TBM head behaviour. The earth pressures acting on the head of shield TBM are investigated according to two different shield jacking force systems (uniform and un-uniform pressure) and several articulation angles. The results obtained from the model tests are analysed. These results will be very useful to understand the shield TBM head interaction behaviour due to the shield jacking operation technique in the shape curved tunnel alignment, and to develop the operation technique.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.7 no.1
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• pp.25-28
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• 1982

A method for finding the symbolic reliability expressision of a conbinational logic circuit is presented. The evaluation of the probabilities of the outputs can be symbolically evaluated by the Boolean operation named sharp operation, provided that every input of such a circuit can be treated as random variables with values set(0, 1) and the output of a circuit can be represented by a Boolean sum of produt expression.

• Journal of Applied Reliability
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• v.6 no.4
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• pp.297-306
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• 2006

In this paper, We presented the algorithm for estimating a reliability between nodes in wireless distributed sensor networks (DSN). To estimate the reliability between nodes, we first modeled DSN as probability graph. Links of the graph are always reliable and the probability of node failure is independent. After all possible simple path which can be established between two nodes are examined, we perform sharp operation to remove repetition event between two nodes. Using probability for each variable of the minimized Boolean equation, we present the reliability formula.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.04a
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• pp.508-512
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• 2004

An ultra-sharp tungsten electrode for field emission was manufactured by using an electrochemical etching method, and its beam characteristics were investigated. KOH and NaOH were the electrolytes used in this research, and the taper length of the tip varied form 150 $\mu\textrm{m}$ to 250 $\mu\textrm{m}$ according to the applied voltage and the concentration of the electrolyte. The electron-beam stability was measured to be within 5% for a total emission current of 5 ${\mu}\textrm{A}$ during 4 hours of operation, and the Ignition voltages were found to be ∼300 V. The tip radius was experimentally found to be 250${\AA}$ from a linear fitting of Fowler-Nordheim plots, which was in remarkably good agreement with that of the image size from scanning ion-microscopy.

• Particle and aerosol research
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• v.7 no.3
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• pp.71-77
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• 2011

Pork belly meat and mackerel are popular meals in Korea. Although a lot of people enjoy cooking these food, there have been some reports that generated organic particles during cooking could be thereas on of lung cancer of nonsmoking housewives. In addition, some experiments show that carcinogens may be included in meat and fishes which we eat usually. For this reason, particle size and concentration in formation during cooking are necessary to figure out the relationship between particles and the diseases. Thus, we identify number concentrations and size distributions of generated nano aerosol in cooking with respect to time, hood operation, and distance between cooking and measurement locations. The maximum concentrations of nano aerosol(diameter sizes are between 10 to 700nm)are decreased after the cooking from $8{\times}10^6{\sharp}/cm^3$ to zeroth order in pork belly meat cooking, and from $3.5{\times}{\times}10^6{\sharp}/cm^3$ to zeroth order in mackerel cooking respectively. When it comes to hood operation during cooking, the detected concentrations of generated aerosols are decreased as in taking flow rate of the hood increases. In cooking pork belly meat, the reduced amount of concentration is about $3{\times}10^6{\sharp}/cm^3$ compared to no hood operation, when hood in taking flow rate is $610m^3/hr$ In mackerel cooking, reduced concentration is $6{\times}10^5{\sharp}/cm^3$ in the same condition. Also, Naphthalene and Fluorene, which are known as polycyclic aromatic hydrocarbons (PAHs), are detected in the generated aerosols during cooking.

• Proceedings of the Safety Management and Science Conference
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• 2008.04a
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• pp.19-33
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• 2008

The study on semiconductor industrial accident in korea has been focused on frequencies of each type, employee, characteristics, cause and un-safety condition, behaviour and so on. Those attributes of semiconductor industrial accidents were usually analyzed independently, so that it was hard to provides a well-process and systematic guide lines for efficient safety management. There fore, there were a few studies based on comprehensive survey in terms of sharp-type of safe management. The questionnaire survey carried out for the workers(284) who were responsible for safety management in to center with corporate company with semiconductor industry the factor analysis showed that there were three factor of safety management. They were 1) Investment and operation and management for accident prevention, 2) Unsafe, safety management 3) General human error and behavior the industries of respondents were correlative with three group. Three Groups showed a statistically significant differences on the number of cases. Actually, the group with the larger investment and the better unsafe cause, human error a of accident prevention had a smaller cause of accident cases.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.695-700
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• 2003

This paper dealt with friction-induced vibrations in engineering practice, specifically arising at the moment of counterturn of two friction surfaces. The harshness of the vibrations are attributed to the sharp change of the friction coefficients from kinetic to static near zero relative velocity, which is one of the examples of the stick slip. But the experimental results and numerical analysis of piston and cylinder operation showed that transition of the friction coefficient from kinetic to static is insignificant in vibrations. Dry friction itself dominates the harshness of vibrations. This study shows that how dry friction triggers the vibrations and demonstrates the effect of sharp transition from kinetic to static friction coefficient on the vibrations.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.3
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• pp.421-435
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• 2017

Recently, due to the saturation of ground structures and the overpopulation of pipeline facilities requires to development of underground structures as an alternative to ground structures. Thus, mechanized tunnel construction of the shield TBM method has been increasing in order to prevent vibration and noise problems in construction of the NATM tunnel for the urban infrastructure construction. Tunnel construction plan for the tunnel line should be formed in a sharp curve to avoid building foundation and underground structures and it is inevitable to develop a shield TBM technology that suits the sharp curve tunnel construction. Therefore, this study is about the structural stability technology of the articulation jack, shield jack and skin plate for the shield TBM thrust in case of the mechanized tunnel construction that is a straight and sharp curve line. The construction case study and shield TBM operation principle are examined and analyzed by the theoretical approach. The torque of the cutter head, the thrust of the articulation jack and the shield jack, the amount of over cutting for curve is important respectively in shield TBM construction of straight and sharp curve line. In addition, it is very important to secure the stability of the skin plate structure to ensure the safety of the inside worker. This study examines the general structure and construction of the equipment, experimental simulation was carried out through numerical analysis to examine the main factors and structural stability of the skin plate structure. The structural stability of the skin plate was evaluated and optimizes the shape by comparing the loads of the articulation jack by selecting the virtual soil to be applied in a straight and sharp curve line construction. Since the present structure and operation method of the shield TBM type in domestic constructions are very similar, this study will help to develop the localized shield TBM technology for the new equipment and the vulnerability and stability review.

• Journal of Chest Surgery
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• v.16 no.1
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• pp.183-190
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• 1983

Pectus Excavatum is a congenital anomaly of the anterior chest wall with a sharp concave curvature of the body of the sternum, from above downward and from side to side, especially just before the junction of gladiolo-xiphoid. We have experienced 14 cases of Pectus Excavatum with several operative procedures, i.e., Ravitch operation in 1 case, Wada operation [Sternal turn-over} in 3 cases, Wada operation and K-wire splint in 5 cases, Modified Wada operation [Rectus Abdominis muscle pedicle attached sternal turn-over] in 5 cases. Nearly all patients developed flail chest treated with internal fixation, and necrotic chondritis was developed postoperatively and treated with excision and curettage in one case with Wada operation. Follow-up Vertebral Index showed 48% preoperatively and 33% postoperatively, average decrement of 15%. We report 14 cases of Pectus Excavatum and their operative treatments.